Which oil?

[ToMang07]

Is there a big difference going to full synthetic on an engine this old? Is 5-40 OK to run it doesn't get real cold around here maybe 3 or 4 times a year under 10 degrees but from november to febuary has been in the mid 20s for the past couple years.I don't know that much about all the diesel oils.Just want something good since I have to have the truck to make money.

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Cost, a full synthetic will just about double your cost for a oil change. On the plus side you can run it longer so it is about a wash. The big thing is that you want to have an analysis done to see how the oil is holding up weather it is synthetic or regular dino and when to change it.

There are really two groups of thought on it. Those that love synthetic and those that like dino. I happen to like dino and really see no need to change over even if it does get down below a -20 at times where I live. Some claim that a switch to a lighter weight oil will cause leaks but I personally think that those leaks were there in the first place but who knows.

The biggest immediate difference I noticed was quicker/easier cold starts with synthetic versus dino oil. My truck had factory Motorcraft 15/40 in it when I got it. I still run 15/40, but because it's synthetic is starts much quicker. That, plus a much higher TBN (Additive package) and it won't sheer as fast allow for longer intervals. At that point the only real factor is the carbon content in the oil, and the only way to check that is with a UOA. I also use Blackstone.

Like bugman said, it's almost a wash after you calculate cost/mile, but I think the synthetic protects better.